Machine element

ABSTRACT

A machine element, in particular for a shaping machine, having a lubricated bearing and/or a seal and at least one drainage conduit for catching a medium issuing from the bearing and/or the seal, preferably substantially pressure-lessly. A collecting device is provided for collecting the medium which is caught in the at least one drainage conduit over a period of time, and a measuring device is adapted to directly and/or indirectly measure an amount of the medium collected by the collecting device over the period of time.

BACKGROUND OF THE INVENTION

The present invention concerns a machine element, in particular for ashaping machine, having a lubricated bearing and/or a seal and at leastone drainage conduit for catching a medium issuing from the bearingand/or the seal, preferably substantially pressure-lessly, in accordancewith the features of the classifying portion of claim 1, and acorresponding method.

The state of the art is illustrated hereinafter by reference to theexample of a rotary feedthrough.

Rotary feedthroughs as are used in particular in shaping machines likefor example injection moulding machines make it possible for mediacirculations, in particular of fluid, that is to say gaseous or liquidmedia, to be transmitted from a component to a shaft which rotates inrelation to the component.

The media passages of those rotary feedthroughs are provided withannular seals on the one hand to prevent the media from issuing from themedia passage and on the other hand to prevent the media beingcontaminated by oil or grease coming from the lubrication for the shaftbearing means.

It will be appreciated that, in dependence on the operating hours of thebearing locations or seals, leakage occurs both in respect of thelubricant and also in respect of the media. Drainage conduits areprovided for that purpose, which open for example into a container.

It is also known in the state of the art to provide pressure sensors inthe drainage conduits. By virtue thereof the operator of theinstallation can be warned if damage to the rotary feedthrough occurs,and as a result larger amounts of lubricant or media issue and possiblycontaminate each other.

Admittedly that system relatively reliably provides information aboutdamage or at least increased leakage at the rotary feedthrough. Ifhowever the pressure in the drainage conduit is already increased therisk of mutual contamination naturally already arises, that is to say ingeneral damage has already occurred.

SUMMARY OF THE INVENTION

The object of the invention therefore is to provide a rotary feedthroughin which impending damage or at least an increase in a leakage rate canalready be detected, as well as providing a corresponding method.

That is effected by at least one collecting device for collecting themedium which is caught in the at least one drainage conduit over aperiod of time, and a measuring device adapted to directly and/orindirectly measure an amount of the medium collected by means of the atleast one collecting device over the period of time.

That is effected by medium issuing from the bearing and/or the sealbeing collected over the period of time and the amount of the mediumcollected over the period of time being directly and/or indirectlymeasured.

The invention can therefore be used not only in rotary feedthroughs butquite generally in relation to machine elements having a lubricatedbearing and/or any machine elements having seals, that is to say inparticular in almost any kind of rolling bearings and/or plain bearings.

The medium which is carried away by the at least one drainage conduitcan be lubricant from the bearing, media in relation to which the sealprovides sealing integrity, or mixtures thereof. In other words,anything which can issue from a seal and/or a bearing is deemed to bemedium in accordance with the invention.

A basic aspect of the invention provides collecting an amount of theissuing medium with the collecting device, which makes it possible tocarry out measurement of the amount with reasonable accuracy. As ingeneral the issuing medium is substantially pressure-less (in comparisonwith the ambient pressure) direct volume flow measurement can normallynot be carried out with acceptable accuracy. (The volume flows can be inthe region of ml/month.)

It is therefore possible by means of the invention to detect increasedleakage at an early time—and thus inter alia also damage to thecorresponding machine component at an early time—. Bearings and/or sealscan thus be subjected to “condition monitoring”.

The apparatus according to the invention can be adapted to measure theamount of the medium collected by means of the at least one collectingdevice during and/or after the period of time, wherein the period oftime is preferably established in advance. For example the at least onedrainage conduit can be shut off by a stop valve and periodicallyemptied by brief opening thereof. If a pressure sensor is available(which is in the normal situation present in any case) it is possible toconclude about the amount of leakage on the basis of the information asto how fast the pressure rises. If for example after emptying of thedrainage conduit the pressure rises significantly faster than waspreviously the case, it is possible to initiate maintenance or a changeof the corresponding machine element.

As a measurement of the leakage rate however it is also possible to usea measured period of time which elapses until a predefined amount of themedium is collected. In particular it can preferably be provided thatthe measuring device is adapted on the one hand to measure a property,that varies with the amount of the collected medium, of the medium whichis collected by means of the at least one collecting device and on theother hand to measure the period of time, wherein a measurement value ofthe period of time at a moment in time at which a measurement value ofthe property of the collected medium reaches and/or exceeds a limitvalue serves as a measurement in respect of the amount of the mediumcollected over the period of time.

That can be achieved for example by a pressure limiting valve. Normalleakage means that the pressure in the at least one drainage conduitrises slowly. If the pressure exceeds the limit pressure of the pressurelimiting valve the valve is opened and the pressure falls in the atleast one drainage conduit. The latter can be detected for example againby way of a pressure sensor or the like. If the frequency at which thepressure limiting valve responds rises it is possible to assume thatthere is increased leakage and maintenance or a change in the machineelement can be initiated.

In general the amount of collected medium, however it is measured, canbe observed, and then maintenance or replacement of the machine elementcan be carried out if the amount per unit of time (or alternatively theperiod of time per unit of amount) rises—significantly—.

Examples of machine elements which can be monitored according to theinvention would be a hydraulic cylinder having at least one sealedpressure chamber or a rotary feedthrough which preferably has aplurality of mutually sealed media conduits.

In particular in the latter case it can be provided that there areseparate drainage conduits for the various media conduits. That howeveris possible not just in relation to rotary feedthroughs. Whenever thereare a plurality of various media or a plurality of various locations atwhich the medium issues on a machine element separate drainage conduitscan be used.

If there are a plurality of (separate) drainage conduits respectiveseparate collecting devices can be associated therewith. In that way itis possible to quickly and easily find out where precisely an increasedleak is occurring.

In a particularly simple configuration the separate drainage conduitscan naturally also be brought together to a main drainage conduit, inwhich case then the at least one collecting device can be arranged inand/or at the main drainage conduit.

The collecting device can have at least one of the following:

a stop valve arranged in the at least one drainage conduit,

a pressure limiting valve arranged in the at least one drainage conduit,and/or

a container connected to the at least one drainage conduit.

In a quite simple configuration however measurement of the collectedmedium could also be implemented by visual checking at a correspondingcollecting container. The measuring device would then be implemented bya viewing window on the corresponding collecting container or by atransparent collecting container.

For the purposes of this document the expression container connected tothe at least one drainage conduit is used to mean any container in whicha fluid of the at least one drainage conduit opens without support fromthe exterior. The possibility has already been mentioned, of providing apressure sensor for detecting a pressure in the at least one drainageconduit and using it as a measuring device in accordance with theinvention.

Protection is also claimed for a shaping machine having a machineelement according to the invention.

Herein, the term “shaping machines” means injection moulding machines,injection presses, presses and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details of the invention will be apparent fromthe Figures and the related specific description.

In the drawing:

FIG. 1a shows a first embodiment of a rotary feedthrough according tothe invention,

FIG. 1b shows a second embodiment of a rotary feedthrough according tothe invention,

FIG. 2a shows an embodiment of a hydraulic cylinder according to theinvention, and

FIGS. 2b and 2c show symbolic views of various configurations of ashaping machine according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The machine element 1 shown in FIG. 1a is a rotary feedthrough or union.It has a plurality of media passages 9 which are sealed off relative toeach other by seals 3.

There are also a plurality of separate drainage conduits 5 which allopen into a main drainage conduit 4.

In that respect it is to be mentioned that the main drainage conduit 4can be composed of a main drainage passage in a component of the rotaryfeedthrough and a flexible or non-flexible conduit portion connectedthereto, like for example a tube or a hose. In the present embodiment astop valve which for example is in the form of a two-way valve serves asthe collecting device 6. A corresponding stop valve can be actuatedelectrically or electronically, in which respect theoretically it isalso possible to use a hand-operated stop valve. In addition there is ameasuring device in the form of a pressure sensor.

The stop valve can be opened at regular intervals and thereafter it ispossible by means of the pressure sensor to observe how quickly thepressure rises. If that occurs significantly faster than in previousobservation cycles it is to be assumed that there is increased leakage.

It is to be noted that not all seals 3, media passages 9 and separatedrainage passages 5 are provided with reference numerals in order tomaintain clarity of the drawing.

FIG. 1b is a view similar to that of FIG. 1a , with the collectingdevice 6 being of a different configuration.

More specifically in FIG. 1b the collecting device 9 is formed by apressure limiting valve. The pressure limiting valve can be set forexample to about 0.5 bar above ambient pressure. When that pressure inthe main drainage conduit 4 is reached the pressure limiting valve opensand the pressure in the main drainage conduit 4 falls—together with theseparate drainage conduits 5. That opening of the pressure limitingvalve can be detected as a drop in pressure by way of the pressuresensor (measuring device 7). If the time between those activations ofthe stop valve decreases significantly it can also be assumed that thereis increased leakage.

FIG. 2a shows an embodiment of the invention, the machine element 1being a hydraulic cylinder having at least one sealed pressure chamber8. At the side of the pressure chamber 8, that is remote from the seal3, the drainage conduit 5 leads away, with pressure medium—in this caseprimarily hydraulic medium from the pressure chamber 8—being caught inthe drainage conduit 5.

The collecting device 6 and measuring device 7 according to theinvention are of a similar structure to the example of FIG. 1 a.Naturally it would also be possible to carry out measurement of theleakage rate as in FIG. 1 b. Further examples are described in relationto FIG. 2 b.

FIG. 2b is a purely diagrammatic view of a shaping machine 10 having amachine element 1 and a drainage conduit 5. Connected to the drainageconduit 5 is a container in which the medium leaking from the machineelement 1 is collected, that is to say the container forms thecollecting device 6. Two examples of possible ways of detecting theamount of medium in the container are illustrated. This would be on theone hand detecting the volume of the medium in the container by way of afloat 7. (It will be appreciated that the level of the float has to bedetected by way of a separate or integrated device. That however is notshown in the diagrammatic view in FIG. 2b .)

The second example would be a weighing device as the measuring device 7,on which the container is arranged. The mass of the medium in thecontainer or a similar value can be detected by the weighing device.

The two embodiments illustrated in FIG. 2b can be used both with ameasuring specification with a previously predetermined period of timeand also with a limit value for the volume or mass.

FIG. 2c diagrammatically shows an embodiment of the invention, wherein amachine element 1 of a shaping machine 10 has a plurality of separatedrainage passages 4. Each separate drainage passage 4 is connected forthat purpose to a combination of collecting device 6 and measuringdevice 7 so that in this embodiment it is possible to preciselyascertain from which of the separate drainage passages 4 an increasedleakage is coming. If an embodiment as shown FIG. 2c is implemented inan embodiment as shown in FIG. 1a or FIG. 1b it would thus be possibleto establish the media passages 9 from which the increased leakage isoriginating.

LIST OF REFERENCES

-   Machine element 1-   Bearing 2-   Seal 3-   Main drainage conduit 4-   Separate drainage conduit 5-   Collecting device 6-   Measuring device 7-   Pressure chamber 8-   Media conduit 9-   Shaping machine 10

1. A machine element, in particular for a shaping machine, comprising alubricated bearing and/or a seal and at least one drainage conduit forcatching a medium issuing from the bearing and/or the seal, preferablysubstantially pressure-lessly, and at least one collecting device forcollecting the medium which is caught in the at least one drainageconduit over a period of time, and a measuring device adapted todirectly and/or indirectly measure an amount of the medium collected bymeans of the at least one collecting device over the period of time. 2.The machine element according to claim 1, wherein the measuring deviceis adapted to measure the amount of the medium collected by means of theat least one collecting device during and/or after the period of time,wherein the period of time is preferably established in advance.
 3. Themachine element according to claim 1, wherein the measuring device isadapted on the one hand to measure a property, that varies with theamount of the collected medium, of the medium which is collected bymeans of the at least one collecting device and on the other hand tomeasure the period of time, wherein a measurement value of the period oftime at a moment in time at which a measurement value of the property ofthe collected medium reaches and/or exceeds a limit value serves as ameasurement in respect of the amount of the medium collected over theperiod of time.
 4. The machine element according to claim 1, wherein themachine element is a hydraulic cylinder having at least one sealedpressure chamber.
 5. The machine element according to claim 1, whereinthe machine element is a rotary feedthrough, preferably with a pluralityof mutually sealed media conduits.
 6. The machine element according toclaim 5, further comprising a plurality of mutually sealed mediaconduits, wherein there are separate drainage conduits for the variousmedia conduits.
 7. The machine element according to claim 1, furthercomprising a plurality of drainage conduits, with which separatecollecting devices are respectively associated.
 8. The machine elementaccording to claim 1, further comprising a main drainage conduit inwhich separate drainage conduits are brought together, wherein the atleast one collecting device is arranged in and/or at the main drainageconduit.
 9. The machine element according to claim 1, wherein the atleast one collecting device has at least one of the following: a stopvalve arranged in the at least one drainage conduit, a pressure limitingvalve arranged in the at least one drainage conduit, and/or a containerconnected to the at least one drainage conduit.
 10. The machine elementaccording to claim 1, wherein the measuring device has a pressure sensorfor detecting a pressure in the at least one drainage conduit.
 11. Ashaping machine having a machine element according to claim
 1. 12. Amethod of determining an amount of a medium issuing over a period oftime from a lubricated bearing and/or a seal, wherein medium issuingfrom the bearing and/or the seal is collected over the period of time,and the amount of the medium collected over the period of time isdirectly and/or indirectly measured.